1. Field of the Invention
This invention relates to a graphic editing system and, more particularly, to a graphic editing system of a so-called CAD system employed for designing semiconductor integrated circuits.
2. Description of the Related Art
Recently, in designing electronic circuits, a computer aided design (CAD) is extensively employed as a design supporting system. For example, designing of semiconductor integrated circuits, such as large scale integrated circuits (LSI) or charge coupled device image sensor (CCD image sensors), consists of functional designing for designing functional specifications of e.g. a large scale integrated circuit, based on system specifications, logical designing for designing a logical circuit based on functional specifications obtained by functional designing and layout designing for designing a so-called mask pattern based on the connection information of the logical circuits obtained by logical designing and verifying the function and characteristics using a simulation system. In each of these designing stages, CAD is employed whenever the necessity arises.
In the layout designing, which is most crucial in designing semiconductor integrated circuits, it is required to render the chip area as small in size as possible under manufacturing process constraints. The layout designing by CAD is roughly classified into an automatic layout designing of automatically arraying and interconnecting cells or functional blocks by an electronic computer and an interactive layout designing carried out in a conversational mode by a designer using a graphic editing system including a graphic display equipped with a pointing device, such as a mouse. After completion of designing of a mask pattern by automatic or interactive layout designing, the functions or characteristics of the semiconductor integrated circuit being designed are simulated based on preset attributes concerning editing objects, such as lines or dots, as determined by manufacturing process conditions.
With the above-described graphic editing system, data concerning coordinates for graphic display or interconnection between the objects are processed independently of a simulating operation. In other words, for performing a simulating operation, it becomes necessary to perform an operation of setting attributes for various editing objects after completion of the mask pattern designing or graphic designing operation. For this reason, it is a frequent occurrence that attribute setting is not made for certain objects through inadvertence and the objects for which attributes have not been set are found out after the start of the simulation operation, producing inappropriate results for the simulation.